Tennessee Red

[Woodrow]

I replaced the coil rail and the spark plugs and the jeep definitely ran better, it is like it now "fires up with half a key turn and just wants to go", of course that is just a "feeling" and not a diagnostic. Anyway, drove it one day and no misfires. Drove it the second day and the check engine light starting flashing intermittently during my drive, I was doing 35mph in 4th gear just cruising, not on the throttle at all. . I could not feel any misfires, I just saw the CEL flashing. It would flash a few times and then quit and then flash a few times and quit.......... When I got home it had a P0300 pending. That was the only code Random Mis-Fire.

This morning (you got to work at night and early morning in this Memphis heat!!). I checked the wire harnesses that run to PCM, to the Cam Pos Sensor and to the Crank Pos Sensor, as well as the one that runs to the injectors and I saw no wear. I then hooked up my scanner and watched the mis-fire count and I had zero at start up, I let the engine warm up and had zero. I then started shaking and pinching the harnesses, watching the misfire count and none. I then used carb cleaner to spray around the throttle body, intake, vacuum lines, etc... and nothing. All runs good.

I was starting to think back to wheeling and I remembered that on the Windrock Trip on Thurs night when it first mis-fired it was also having a high idle. It was idling around 900-1000 RPMs in lieu of around the 600 RPMs that it normally did. It only did this for a short period of time and seemed to occur prior to the misfires starting. It never did it again the entire weekend or since then. Based on this, I again checked for vacuum leaks, but none could be found. Again, just capturing info for future reference, not sure if it means anything.

Scanner and TPS question for anyone who may know? How does the scanner bump up the RPMs with a cable throttle? My understanding is that the TPS only provides a signal to the PCM. So how does it bump up the RPMs? When I did the cam synch procedure, it definitely bumps up the RPMs to 1000 RPM during the test, so I know it does it. But when I went into the scanner and selected to actuate the RPMs to 2000 RPMs, I could here a slight change in RPM but it did not take it to 2000 RPM and it actually went down slightly? Weird?

Following. Do you think this is all related to the problems you were having intermittently in Moab? Definitely some weirdness here. I'll be happy when you put this to bed Victor.

 

[Wildman]

I replaced the coil rail and the spark plugs and the jeep definitely ran better, it is like it now "fires up with half a key turn and just wants to go", of course that is just a "feeling" and not a diagnostic. Anyway, drove it one day and no misfires. Drove it the second day and the check engine light starting flashing intermittently during my drive, I was doing 35mph in 4th gear just cruising, not on the throttle at all. . I could not feel any misfires, I just saw the CEL flashing. It would flash a few times and then quit and then flash a few times and quit.......... When I got home it had a P0300 pending. That was the only code Random Mis-Fire.

This morning (you got to work at night and early morning in this Memphis heat!!). I checked the wire harnesses that run to PCM, to the Cam Pos Sensor and to the Crank Pos Sensor, as well as the one that runs to the injectors and I saw no wear. I then hooked up my scanner and watched the mis-fire count and I had zero at start up, I let the engine warm up and had zero. I then started shaking and pinching the harnesses, watching the misfire count and none. I then used carb cleaner to spray around the throttle body, intake, vacuum lines, etc... and nothing. All runs good.

I was starting to think back to wheeling and I remembered that on the Windrock Trip on Thurs night when it first mis-fired it was also having a high idle. It was idling around 900-1000 RPMs in lieu of around the 600 RPMs that it normally did. It only did this for a short period of time and seemed to occur prior to the misfires starting. It never did it again the entire weekend or since then. Based on this, I again checked for vacuum leaks, but none could be found. Again, just capturing info for future reference, not sure if it means anything.

Scanner and TPS question for anyone who may know? How does the scanner bump up the RPMs with a cable throttle? My understanding is that the TPS only provides a signal to the PCM. So how does it bump up the RPMs? When I did the cam synch procedure, it definitely bumps up the RPMs to 1000 RPM during the test, so I know it does it. But when I went into the scanner and selected to actuate the RPMs to 2000 RPMs, I could here a slight change in RPM but it did not take it to 2000 RPM and it actually went down slightly? Weird?

I HATE trying to find intermittent issues. They are always a PITA to chase down. I hope you've got it fixed and don't have anymore issues.


From what I know it's using the IAC to change the idle RPM. There was a company that sold a electronic idle speed controller that was based off the IAC.

Of course I can't find the website anymore...

 

[sab]

Drove it the second day and the check engine light starting flashing intermittently during my drive, I was doing 35mph in 4th gear just cruising, not on the throttle at all.

A loose timing chain can cause misfires under low loads.

Scanner and TPS question for anyone who may know? How does the scanner bump up the RPMs with a cable throttle? My understanding is that the TPS only provides a signal to the PCM. So how does it bump up the RPMs? When I did the cam synch procedure, it definitely bumps up the RPMs to 1000 RPM during the test, so I know it does it. But when I went into the scanner and selected to actuate the RPMs to 2000 RPMs, I could here a slight change in RPM but it did not take it to 2000 RPM and it actually went down slightly? Weird?

I don't believe that a scan tool can raise the idle to 2000 rpm. High idle (1000 rpm) is likely accomplished using the Idle Air Controller, but that's just a guess...

 

[sab]

From what I know it's using the IAC to change the idle RPM. There was a company that sold a electronic idle speed controller that was based off the IAC.

Of course I can't find the website anymore...

And Rick beat me to it.

 

[gasiorv]

A loose timing chain can cause misfires under low loads.

Yep, that is where I am going next. Figured I would try to rule out all the electrical/sensors before going after the mechanical.

 

[gasiorv]

Following. Do you think this is all related to the problems you were having intermittently in Moab? Definitely some weirdness here. I'll be happy when you put this to bed Victor.

Don't think it is related. I had a heat soak issue in Moab but it never mis-fired or through any P030x codes. It would just shut down when it got super hot from working it on an obstacle. Now, I don't have the heat soak issue it is strictly a random mis-fire. Related or coincidence? Whatever, I just want to figure it out so I am not having to worry about it out on the trail.

 

[gasiorv]

Installed new timing chain this morning. The old one definitely had some slack. Not sure if it was leading to valve train issues or not, I will have to drive it a while and see. Funny thing is, I have been driving the jeep for the past week or so and it never had a mis-fire code thrown?

Thanks to Irun for posting THIS about the oil slinger being deleted. I knew I didn't remove one but when I went to reinstall I looked at the Service Manual and it was calling one out which had me confused.

Also changed the front crankshaft seal in the timing cover and the harmonic balancer had a pretty good groove where the seal was riding so I replaced it as well in lieu of doing the repair sleeve.

Video of the slack before and after:

 

[Rickyd]

Have you hooked a good ol fashioned vacuum gauge and read the directions for different needle actions?

 

[gasiorv]

Have you hooked a good ol fashioned vacuum gauge and read the directions for different needle actions?

I have not. Since it started as a heat soak issue and then became a misfire issue I just assumed that the fix for the heat soak induced the mis-fire which is why I was so focused on sensors. If the timing chain didn't fix it (which I am hopeful), then I will just have to go back to basics and start diagnosing in lieu of just throwing parts at it based on an assumption.

 

[Rickyd]

I have not. Since it started as a heat soak issuured cheap and quicke and then became a misfire issue I just assumed that the fix for the heat soak induced the mis-fire which is why I was so focused on sensors. If the timing chain didn't fix it (which I am hopeful), then I will just have to go back to basics and start diagnosing in lieu of just throwing parts at it based on an assumption.

I just figured it's cheap and quick. And sometimes helps give direction.

I found a timing belt that had slipped one tooth once with a vacuum gauge.

 

[gasiorv]

Still chasing this random misfire issue. Yesterday it flashed the CEL multiple times on my way home from Grocery Getting. I was just cruising around 35mph with RPMs at 2000 (I looked when I saw the light start to flash). It flashed a few times, stopped, and then a few moments later flashed a few more times with no change in the driving.
When I got home I checked the codes and when I went into the "Jeep" module on my scanner it showed P0300 with no freeze frame data. When I just went to standard OBDII, it showed P0300 and had the following freeze frame:
Calculated Engine Load - 86.7%
Coolant Temp - 195.80 deg.
STFT(1) - -2.34%
LTFT(1) - -0.78%
STFT(2) - 0.00
LTFR(2) - -0.78%
Intake Manifold Abs Pressure - 12.91 psi
RPM - 3776 RPM

What throws me is the RPM and calculated engine load? I actually think this freeze frame data is from a previous occurrence, a few days earlier I got on it a little while pulling out onto a main road and the CEL flashed 1 or 2 times, but when I got home and checked for codes I only used the Jeep Module on my scanner and there was no misfire codes, I never checked the generic OBDII, but it may have been there.

Now, I know last week when I was at idle in my garage I had a positive LTFT which is approaching 10% and when I would increase the RPMs the LTFT would quickly go to zero. So I think I have a vacuum leak somewhere and have been looking but I can't find it with propane (going to have to fire up a cigar and see if I can find it with smoke).

But after I got home yesterday and checked the freeze frame data, I also checked the live data at idle and I was getting:
STFT(1) - +5.47%
LTFT(1) - +5.47%
STFT(2) - +5.47%
LTFR(2) - +3.91%

So with the STFT, it is slightly correcting for a lean condition (way within the 10%), but it is relearning because the week before at idle I had stable LTFT at approx +8% and zero STFT. Still indicator of vacuum leak (or possible exhaust leak before O2 pulling in oxygen, or less likely upstream O2 sensors).

It is crazy that it runs fine in the garage at idle and it actually runs fine when driving, I don't think it is misfiring at all, but the PCM is getting an indication that there is a misfire from a sensor(s). If there was no fear of it going into limp mode I would just ignore this issue all together because it is running great. But I can't have it detecting misfire and going into limp mode (like it did to me in the past).

 

[JMT]

@gasiorv

PCM?

 

[gasiorv]

This is with my original PCM installed. I do have a spare wranglerfix pcm and it still occurs with the spare PCM, so I don't think it is a PCM issue.

 

[Apparition]

Still chasing this random misfire issue. Yesterday it flashed the CEL multiple times on my way home from Grocery Getting. I was just cruising around 35mph with RPMs at 2000 (I looked when I saw the light start to flash). It flashed a few times, stopped, and then a few moments later flashed a few more times with no change in the driving.
When I got home I checked the codes and when I went into the "Jeep" module on my scanner it showed P0300 with no freeze frame data. When I just went to standard OBDII, it showed P0300 and had the following freeze frame:
Calculated Engine Load - 86.7%
Coolant Temp - 195.80 deg.
STFT(1) - -2.34%
LTFT(1) - -0.78%
STFT(2) - 0.00
LTFR(2) - -0.78%
Intake Manifold Abs Pressure - 12.91 psi
RPM - 3776 RPM

What throws me is the RPM and calculated engine load? I actually think this freeze frame data is from a previous occurrence, a few days earlier I got on it a little while pulling out onto a main road and the CEL flashed 1 or 2 times, but when I got home and checked for codes I only used the Jeep Module on my scanner and there was no misfire codes, I never checked the generic OBDII, but it may have been there.

Now, I know last week when I was at idle in my garage I had a positive LTFT which is approaching 10% and when I would increase the RPMs the LTFT would quickly go to zero. So I think I have a vacuum leak somewhere and have been looking but I can't find it with propane (going to have to fire up a cigar and see if I can find it with smoke).

But after I got home yesterday and checked the freeze frame data, I also checked the live data at idle and I was getting:
STFT(1) - +5.47%
LTFT(1) - +5.47%
STFT(2) - +5.47%
LTFR(2) - +3.91%

So with the STFT, it is slightly correcting for a lean condition (way within the 10%), but it is relearning because the week before at idle I had stable LTFT at approx +8% and zero STFT. Still indicator of vacuum leak (or possible exhaust leak before O2 pulling in oxygen, or less likely upstream O2 sensors).

It is crazy that it runs fine in the garage at idle and it actually runs fine when driving, I don't think it is misfiring at all, but the PCM is getting an indication that there is a misfire from a sensor(s). If there was no fear of it going into limp mode I would just ignore this issue all together because it is running great. But I can't have it detecting misfire and going into limp mode (like it did to me in the past).

When I had misfire codes it was my cats. Happened in the middle of nowhere Nebraska, I changed plugs and coil rail at oreilly's thinking that was the issue. Figured out if I stayed under 55 mph (This was likely not the limit but the engine load at that speed) I could keep driving without going into limp mode so we drove all the way home and I figured out the next day it was the cats. Haven't had that issue since swapping in the flowmaster system.

All that said, have you checked your cats?

 

[gasiorv]

I have not checked my cats because I have not had any restricted power issues, I can bounce this thing off the rev limiter all day. But I will add it to my list, i only have the pre cats and if they're clogged I have no issue with just figuring out how to open them up, I am not worried about downstream o2 sensors.

 

[Woodrow]

I have not checked my cats because I have not had any restricted power issues, I can bounce this thing off the rev limiter all day. But I will add it to my list, i only have the pre cats and if they're clogged I have no issue with just figuring out how to open them up, I am not worried about downstream o2 sensors.

I didn't know these PCMs had limp mode. But I also didn't know about the rev limiter until hit it the other day (5200 in mine).

 

[gasiorv]

N

I didn't know these PCMs had limp mode. But I also didn't know about the rev limiter until hit it the other day (5200 in mine).

Not sure what rpm it is, too busy holding on and praying. But I know the sound.

 

[gasiorv]

Well, this thing is running great, probably better than it has in a long time. But it is still throwing the P0300 code randomly. I have been driving it to work and it seems to flash the CEL at least once during the 45 minute trip, sometimes more than once, but it never actually misfires. I don't hear it misfire and I don't feel it and it is running strong. It is completely random too, sometimes when I am accelerating hard and sometimes when I am coasting to stop and everything in between. Freeze frame data that it captures is not much and looks good. It has good compression, it has good vacuum, vacuum reacts as should with throttle, etc... new spark plugs, ignition rail, put in the original OEM injectors, cats are clear, good fuel pressure, new CPS, new CMS, I inspected wire harnesses, recalibrated the CMS/CPS synch, new timing chain, smoke tested and found no vacuum leaks, and I installed a PCM. Same issue, get a P0300 and it flashes the CEL but it never actually misfires, the PCM is just seeing something that it interprets as a misfire.

I can't get it to misfire or sense a misfire in the garage which is what is irritating. I have not done a cylinder leak down check yet (don't have that tool) but vacuum check doesn't have any needle bounce at all and what I can see with valve cover off looks good.

I am pretty much over it, I have been driving it for the last three days to work and back (45 min of city and suburb driving each way) and it drives great, when the CEL does flash it is not throwing it into limp mode, so I am just going to run it as is. When I hit the trails next week, I will just carry a scanner with me to clear the code if it does happen to go into limp mode. Anyone who wants to do some good rock technical wheeling, we will be in Oklahoma at RMR Sept 25, come on.

 

[JMT]

Well, this thing is running great, probably better than it has in a long time. But it is still throwing the P0300 code randomly. I have been driving it to work and it seems to flash the CEL at least once during the 45 minute trip, sometimes more than once, but it never actually misfires. I don't hear it misfire and I don't feel it and it is running strong. It is completely random too, sometimes when I am accelerating hard and sometimes when I am coasting to stop and everything in between. Freeze frame data that it captures is not much and looks good. It has good compression, it has good vacuum, vacuum reacts as should with throttle, etc... new spark plugs, ignition rail, put in the original OEM injectors, cats are clear, good fuel pressure, new CPS, new CMS, I inspected wire harnesses, recalibrated the CMS/CPS synch, new timing chain, smoke tested and found no vacuum leaks, and I installed a PCM. Same issue, get a P0300 and it flashes the CEL but it never actually misfires, the PCM is just seeing something that it interprets as a misfire.

I can't get it to misfire or sense a misfire in the garage which is what is irritating. I have not done a cylinder leak down check yet (don't have that tool) but vacuum check doesn't have any needle bounce at all and what I can see with valve cover off looks good.

I am pretty much over it, I have been driving it for the last three days to work and back (45 min of city and suburb driving each way) and it drives great, when the CEL does flash it is not throwing it into limp mode, so I am just going to run it as is. When I hit the trails next week, I will just carry a scanner with me to clear the code if it does happen to go into limp mode. Anyone who wants to do some good rock technical wheeling, we will be in Oklahoma at RMR Sept 25, come on.

RMR looks fun. Reminds me more of the terrain I wheeled in central TX, and I'm from N of Paris, TX, and more near Powderly which is only about 5 miles from OK. Look out for them Cherokee's!

I interpret all that as good news about your rig.

 

[gasiorv]

Well after my post on Wednesday, I continued to drive the jeep and on my way to meet up with others for a Mt bike ride that evening the CEL started flashing and it went into limp mode. I pulled over and shut it down and restarted it and the limp mode was cleared and I was able to continue driving. Next morning I checked the codes and in addition to the p0300 I also had p0301, 303, 304, 305, 306 the old #2 cylinder code was pending. So the actual individual cylinder code is what must have the computer shut down the injectors to the cylinders and go into limp mode. Anyway, I installed a new Standard Motors CPS that I bought as a trail spare and drove it all day Thursday with no issues at all, so I am thinking that the MOPAR CPS that I installed was actually the culprit.
So -
Heat sink issue while in Moab and I changed the CPS (change number 1)
Heat sink issue continues but it now also throws cam/synch loss of signal and other random codes.
Change CPS and CMS (change number 2)
Heat sink issue goes away and I then had the misfire issue. After extensive troubleshooting and changing of other parts I eventually change the CPS (change number 3) and fingers crossed it is the fix.

So odd that the first replacement CPS would also result in the heat sink issue? Also so odd that the 2nd replacement which was a $133 MOPAR brand resulted in the misfire code issue. Apparently Mexicans can make great food, but they suck at assembling electronic components. So wish me luck that I this is a good fix and plan on changing your sensors 3 times to get a good one.